MP Barnaby Joyce has once again called for a royal commission into Australia's largest supermarket chains, and in the process thrown down the gauntlet to Coles.

"It's over to you Coles if you want to keep playing this game," Mr Joyce said, while visiting the NSW South Coast town of Nowra in his capacity as special envoy for drought.

"I'm a backbencher I don't care, and I've got a lot of backbencher mates who support me on this one.

Mr Joyce commended Woolworths for their decision to raise the price of milk to $1.10 and said it was "a disgrace" that Coles had not followed suit.

"I literally have contempt when I see their $2 two-litre milk on the shelf. I make a point of finding something else. If you can't afford another 20 cents, honestly don't give me that tripe," he said.

"We tried talking to Coles for so long and they just don't seem to listen, so let's try another avenue. Let's try a royal commission, and I'll be happy to see them all turn up to that and maybe they can explain it clearer to them than they can to us.

"I also believe we should have a general divestiture power, because that always works once you tell them they could be broken into two, that seems to get their attention."

Outgoing MP Ann Sudmalis announced her resignation from the seat in September amid claims of bullying, and branch-stacking.

"Ann Sudmalis was a good person. I respected her greatly, and to follow on from her work and Joanna Gash before her, we want to make sure we build on their great work, and deliver even more," Mr Joyce said.

"Katrina Hodgkinson, I strongly believe, is the person with the character, capabilities and understanding to do precisely that."

Intense speculation followed as to who would become the endorsed candidate for the South Coast seat, which sits on a knife's edge - Ms Sudmalis claimed only a narrow victory in the 2016 election over Labor candidate Fiona Phillips, herself from a well-known dairying family.

Endorsed Liberal Grant Schultz was brushed aside by the party, when Warren Mundine was parachuted into the race by Prime Minister Scott Morrison. Mr Schultz has since resigned from the party and will run as an independent.

Mr Joyce's strong stance against the supermarket giants follows NSW National Party leader and Deputy Premier John Barilaro's request for the Feds to keep quiet, to avoid ruining their state election campaign.

Asked if Mr Barilaro's comments were productive for her campaign, Ms Hodgkinson said she would continue on her campaign trail.

"What I'm doing at the moment is trying to get around to as many community groups as I can and get a good grip on the grassroots issues, the things that really affect people from all walks of life, and I will continue to do that," she said.

"This is part of my listening tour, if any member of parliament wants to join me, then I welcome them with open arms because I want people in government to see what's happening on the South Coast.

"I'm thrilled Michael McCormack came to Moruya recently and announced my preselection, and to have Barnaby here today."

Ms Hodgkinson reaffirmed her position as a candidate in a seat not held by a National Party member in more than 15 years.

"The Nationals are running in Gilmore," she declared.

"And I want as many of our MPs as possible to get to know the district, to understand the district, and to be contributing out of their portfolios into this district," she said.

"The important thing today was to talk face-to-face with the dairy farmers and to listen to each of their unique concerns."